MATLAB: How do i create a program that tell me how many numbers i got after point in A decimal number

decimal number

for example for 3.14159265358979 the answer is 14

Best Answer

https://www.mathworks.com/matlabcentral/answers/184255-how-to-calculate-digits-after-decimal-point#answer_172122

https://www.mathworks.com/matlabcentral/answers/10795-counting-the-number-of-digits#answer_14856

https://www.mathworks.com/matlabcentral/answers/52590-find-the-number-of-digits-after-the-decimal-point-in-a-number-please-help

https://www.mathworks.com/matlabcentral/answers/142819-how-to-find-number-of-significant-figures-in-a-decimal-number#answer_145894

Related Solutions

MATLAB: How to calculate digits after decimal point

See this related thread:

http://www.mathworks.com/matlabcentral/answers/142819-how-to-find-number-of-significant-figures-in-a-decimal-number

Using the function in the above link, the number of significant digits after the decimal point could be calculated as follows:

max(sigdigits(x)-floor(log10(abs(x)))-1,0) % Don't count sig digits before decimal pt

EDIT:

If you want to add a digit after the last significant digit, then something like this (assumes x is positive):

x = original_number; % E.g., 123.456
a = added_digit;  % E.g., 9
y = x + a*10^(floor(log10(x))-sigdigits(x)); % New number

E.g.,

>> x = 123.456
x =
     1.234560000000000e+02
>> a = 9
a =
     9
>> y = x + a*10^(floor(log10(x))-sigdigits(x))
y =
     1.234569000000000e+02
>> x = 1.23456789123
x =
   1.234567891230000
>> a = 9
a =
     9
>> y = x + a*10^(floor(log10(x))-sigdigits(x))
y =
   1.234567891239000
>> x = 12345.12345
x =
     1.234512345000000e+04
>> a = 8
a =
     8
>> y = x + a*10^(floor(log10(x))-sigdigits(x))
y =
     1.234512345800000e+04

MATLAB: Is floor(2.00000000) giving me a result of 1

If the number is displaying as 2.0000... on the screen, it isn't exactly 2 but it is close to 2. If a number is exactly 2 it will display as 2 without the 0's past the decimal point printed. So you apparently have done some calculations that result in a number that is very slightly less than 2.

Basically, the result of your floating point calculations cannot be represented exactly in IEEE double precision arithmetic. So this is leading to your problem. E.g., your calculations with the exact decimal conversions shown (note that 1.2 and 0.2 cannot be represented in IEEE double precision exactly):

>> mul = 2*6
mul =
    12
>> XVY = 10
XVY =
    10
>> XVZ = mul/XVY
XVZ =
    1.2000
>> XVZ_1 = floor(XVZ)
XVZ_1 =
     1
>> XVW = 1.2 - XVZ_1
XVW =
    0.2000
>> T1 = XVW*10
T1 =
    2.0000    <-- 0's printing after decimal point means number is not exactly 2
>> floor(T1)
ans =
     1
>> num2strexact(XVZ)
ans =
1.1999999999999999555910790149937383830547332763671875
>> num2strexact(XVW)
ans =
0.1999999999999999555910790149937383830547332763671875
>> num2strexact(T1)
ans =
1.999999999999999555910790149937383830547332763671875

Best Answer

Related Solutions

MATLAB: How to calculate digits after decimal point

MATLAB: Is floor(2.00000000) giving me a result of 1

Related Question